Background and objective: We have investigated whether, after major abdominal Surgery, the addition of remifentanil to tramadol for intravenous patient-controlled analgesia improved analgesia and lowered pain scores, compared to a patient-controlled analgesia containing only tramadol. Methods: Sixty-two patients were allocated randomly to receive an intravenous patient-controlled analgesia with tramadol alone (T), or tramadol plus remifentanil (TR), in a double-blind randomized study. Whenever patients complained of pain, they were allowed to use bolus doses of tramadol (0.2 mg kg(-1)) or tramadol (0.2 mg kg(-1)) plus remifentanil (0.2 mu g kg(-1)) mixture every 10 min Without a time limit and background Infusion. Discomfort, sedation, pain scores, total and bolus patient-controlled analgesia tramadol consumption, and side-effects were recorded for up to 24 h after the start of patient-controlled analgesia. Results: Pain scores at rest were statistically significantly lower in the TR group at 6, 12 and 24 h than in T group (P < 0.05). Pain scores at movement and patient comfort scores were also found to be significantly lower in the TR group at 2, 6, 12 and 24 h than in the T group (P < 0.05). Although the TR group consumed less tramadol, there were no statistically significant differences in the Cumulative tramadol consumptions between the groups at any time. However, the number of patients requiring rescue analgesia and average supplementary doses used was significantly higher in the T group than in the TR group (P < 0.05). Conclusions: After major abdominal Surgery, adding remifentanil (0.2 mu g kg(-1)) to tramadol (0.2 mg kg(-1)), with 10-min lockout times, for patient-controlled analgesia offered better postoperative pain relief and patient comfort, without causing any sedation or respiratory depression.